An Evolved Packet System (EPS) of the 3rd Generation Partnership Project (3GPP) is composed of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), a Mobility Management Entity (MME), a Serving Gateway (S-GW), a Packet Data Network Gateway (P-GW or PDN GW), a Home Subscriber Server (HSS), a 3GPP Authentication Authorization Accounting (AAA) server, a Policy and Charging Rules Function (PCRF) entity and other supporting nodes.
FIG. 1 is a schematic diagram of system architecture of EPS. As illustrated in FIG. 1, the MME is responsible for the related work of a control plane, such as the mobility management, processing of Non-Access stratum signaling and management of the user mobility management context and so on; an access gateway comprises a S-GW and a P-GW, wherein the S-GW is an access gateway device connected with the E-UTRAN, which forwards data between the E-UTRAN and the P-GW and is responsible for performing buffering on the paging waiting data; and the P-GW is a border gateway of the EPS and the packet data network (PDN), which is responsible for functions such as the access of the PDN and forwarding data between the EPS and the PDN and so on; an authentication authorization server comprises a HSS and a 3GPP AAA and so on; the PCRF is a policy and charging rules function entity which is connected with the IP service network of an operator through a receiving interface Rx and obtains the service information, and additionally the PCRF is connected with the gateway devices in the network through Gx/Gxa/Gxc interfaces and is responsible for initiating the establishment of IP bearer, ensuring the Quality of Service (QoS) of the service data and performing the charging control.
As a new kind of access service way, a home base station is a small and low-power base station, which is deployed in indoor locations such as home and office and so on, and the main function is to provide a higher service rate for the user and lower the cost required for use of high rate service and meanwhile make up for the lack of coverage of the existing distributed cell radio communication system. The advantages of a home base are cost-effectiveness, convenience, low-power output and Plug and Play and so on.
The home base station can be directly connected to a core network and, as illustrated in FIG. 1, can also access the core network by a logical network element, that is a home base station gateway, wherein the main functions of the home base station gateway are verifying the security of the home base station, processing registration of the home base station, performing operation, maintenance and management of the home base station, configuring and controlling the home base station according to the requirements of the operator, and taking charge of exchanging data between the core network and the home base station. The access gateway can be a S-GW, a P-GW, a Serving GPRS Support Node (SGSN), or a Gateway GPRS Support Node (GGSN). The local access gateway can be a Local SGW (L-SGW), a local PGW (L-PGW), a Virtual SGW (V-SGW), a Virtual PGW (V-PGW), or a Local GGSN (L-GGSN) and can also be a traffic offload function entity. The local access gateway can be collocated with a radio side network element together or can be set in the vicinity of the radio side network element, and can also be collocated with the home base station gateway together or can be set in the vicinity of the home base station gateway.
FIG. 2 is a schematic diagram showing a data flow path of local IP access and traditional core network IP access. As illustrated in FIG. 2, in order to achieve the Local IP Access (LIPA) function and to make the UE achieve local access to other IP devices in the home network or local access to internet, a local access gateway is added, which may provide powerful support to the local IP access technology, wherein the local access gateway can be collocated with a radio side network element together or can be set in the vicinity of the radio side network element, and can also be collocated with a home base station gateway together or can be set in the vicinity of the home base station gateway. As for users supporting the local IP access, a traditional core network IP access data path and a local IP access data path can be established. As for a LIPA connection, the local IP access data path is from the UE to the radio side network element/home base station gateway to the local access gateway (L-SGW, L-PGW), but the data transmission is not through the core network. In order to make UE achieve the local access to other IP devices in the home network or the local access to internet, two connections can be established, wherein the first local IP access data path directly accesses the internet (an internet LIPA connection), and the second local IP access data path directly accesses other IP devices of the home network (a home network LIPA connection).
The UE user can actively apply for establishing a LIPA connection according to its own will, for example, notifying the core network that it is required to establish a LIPA connection by using a particular access point name, and at that time the mobility management element judges whether a LIPA connection can be established for that application of user according to user subscription, or the capability of radio side network element/home base station gateway. If the LIPA connection cannot be established, a core network connection can be directly established. The UE can also use a normal access point name to initiate services, and the mobility management element directly decides whether to establish the LIPA connection or the core network connection for the application of user according to the operator's policy, subscription, or the capability of radio side network element/home base station gateway. After deciding to establish the LIPA connection for the user, the mobility management element also needs to check whether the LIPA connection established for the user supports mobility (i.e. service continuity).
However, the UE does not know the type of the current connection, that is, the UE does not know whether the current connection is the local IP access connection or the core network connection. If it is the local IP access connection, the UE also does not know whether the local IP access connection supports mobility. When the UE needs to initiate service requests after moving in the idle state, only the core network connection or the LIPA connection supporting mobility can be activated. After handover, only the core network connection or the LIPA connection supporting mobility can be relocated to a new base station. However, as for the LIPA connection that does not support mobility, the UE can reestablish it in a new base station. Therefore, the UE needs to know which of the established connections are LIPA connections and which LIPA connection does not support mobility so as to complete suitable operation after the UE moves.